I have a simple Darlington circuit that can operate anywhere between 3v and higher. I want to run it using a 9v battery. Would I lengthen the life of the battery by using a zener to decrease battery output to 6v or less?

 

No. Any excess energy is wasted as heat generated in the zener.
What you need is an efficient DC-DC converter that drops the 9VDC down to 3VDC.

 

What does the circuit do?

 

It's a dual channel touch detector, output of each channel also signaled by an LED.

 

No. Any excess energy is wasted as heat generated in the zener.
What you need is an efficient DC-DC converter that drops the 9VDC down to 3VDC.

Thanks for the fast reply. DC-DC converters appear to be rather expensive, much cheaper to replace battery when needed!